1. Field of the Invention
This invention relates in general to well drilling and production equipment, and in particular to a drill-through spool body sleeve assembly for testing the spool body transverse bores and valves and for protecting the spool body during drilling operations.
2. Description of the Related Art
A well capable of producing oil or gas will have a conductor housing secured to a string of conductor pipe, the conductor pipe extending a short depth into the well. A wellhead housing then is landed in the conductor housing. The wellhead housing is secured to an outer or first string of casing. The first string of casing extends through the conductor to a deeper depth into the well. Depending on the particular conditions of the geological strata above the target zone (typically, either an oil or gas producing zone or a fluid injection zone), one or more additional casing strings will extend through the outer string of casing to increasing depths in the well until the well is cased to its final depth. Each string of casing is supported at the upper end by a casing hanger. The casing hanger lands in and is supported by the wellhead housing.
In typical wells, multiple strings of casing are suspended within the wellhead housing to achieve structural support for the well to the depth of the target zone. Where multiple strings of casing are set within the outer casing, multiple casing hangers are landed in the wellhead housing, each set above the previous one in the wellhead housing. Between each casing hanger and the wellhead housing, a casing hanger seal assembly is set to isolate each annular space between strings of casing. The last, and innermost, string of casing extends into the well to the final depth, this being the production casing. The strings of casing between the outer casing and the production casing are typically referred to as intermediate casing strings.
When drilling and running strings of casing in the well, it is critical that the operator maintain pressure control of the well. This is accomplished by establishing a column of fluid with predetermined fluid density inside the well. During drilling operations, this fluid is circulated down into the well through the inside of the drill string out the lower terminal end of the drill string and back up the annulus around the drill string to the surface. This column of density-controlled fluid balances the downhole pressure in the well. When setting casing, the casing is run into the pressure balanced well and then cemented in place.
A blowout preventer system (BOP) is employed during drilling and running strings of casing in the well as another safety system to ensure that the operator maintains pressure control of the well. The BOP is located above the wellhead housing by running it on a drilling riser to the wellhead housing.
After drilling and installing the casing strings is complete, the well must be completed for production. In the well, the production fluids flow through perforations made in the production casing at the producing zone. A string of production tubing extends to the producing zone within the production casing to provide a pressure-controlled conduit through which the well fluids are produced. At some point above the producing zone, a packer seals the space between the production casing and the production tubing to ensure that the well fluids flow through the production tubing to the surface. The tubing is supported by a tubing hanger assembly that lands and locks above the production casing hanger.
At the wellhead, various arrangements of production control valves are arranged in an assembly generally known as a tree. In some wells, a vertical tree is installed on the wellhead housing. First, the production hanger and production tubing are installed in the wellhead housing. Then, the BOP is removed and then the vertical tree is locked and sealed onto the wellhead housing. The vertical tree has one or more production bores containing actuated valves and extending vertically to respective lateral production fluid outlets in the wall of the vertical tree. The production bores and production valves are in-line with the production tubing. An example of a vertical tree would include a monobore vertical tree.
Using vertical trees involves problems, however. If it is necessary to pull the completion, consisting essentially of the tubing string and tubing hanger, the vertical tree needs to be removed and replaced by the BOP. However, replacing the BOP involves setting and testing plugs or relying on downhole valves, which may be unreliable by not having been used or tested for a long time. The well is also in a vulnerable condition while the vertical tree and BOP are being exchanged and neither one is in position, which is a lengthy operation. This usually involves plugging and/or killing the well.
In addition, installing the production hanger and production tubing in the wellhead housing can involve problems. For example, the wellhead housing seal bore in the area where the production hanger lands could be damaged. A damaged wellhead housing could cause significant problems because wellhead housings are not able to be retrieved once installed. Also, the wellhead housing may not be compatible for connection with the vertical tree. In addition, the wellhead may have been installed at an undesirable elevation. Also, the wellhead may not have sufficient room for a tubing hanger due to the number of casing hangers installed in the wellhead.
To alleviate some of the problems associated with installing the production hanger and production tubing in the wellhead housing, a spool body may be installed between the vertical tree and the wellhead housing. With a spool body, the production hanger and production tubing are installed in the spool body instead of the wellhead housing.
One example of a spool body is a tubing spool. The tubing spool provides an undamaged bore in which the production hanger and tubing may be installed. It may also act as an adapter with its lower terminal end compatible with the wellhead housing and its upper terminal end compatible with the lower terminal end of the vertical tree. It can also locate the tree at a more desirable elevation. A tubing spool also can provide a position for the tubing hanger in the event there is none in the wellhead housing. When drilling the well, the tubing spool is installed after the production casing has been installed in the wellhead. This requires that the BOP must first be removed from the wellhead before installing the tubing spool. After the tubing spool is installed, the BOP is then installed onto the tubing spool. After, the production hanger and production tubing is installed in the tubing spool, the BOP is removed and the vertical tree is installed onto the tubing spool.
Thus, the tubing spool, while alleviating some of the problems associated with using a vertical tree alone, still leaves the well in a vulnerable condition while the tubing spool and BOP are being exchanged and neither one is in position. Also, if it is necessary to pull the completion, consisting essentially of the tubing string and tubing hanger, the vertical tree needs to be removed and replaced by the BOP.
Another example of a tubing spool is a drill-through tubing spool, which is a type of drill-through spool body. The drill-through tubing spool is installed on the wellhead housing at the point when a BOP is needed for drilling. The drill-through tubing spool has a large through bore capable of passing equipment through the tubing spool bore. Thus, the drill-through tubing spool provides the additional benefit of eliminating the need to make multiple BOP trips.
However, the drill-through tubing spool also presents problems to the drilling and completion operations. The drill-through tubing spool includes transverse bores with respective valves that all need to be pressure tested not only at production operation pressures, but also drilling operation pressures. The pressure tests can be performed before and/or after the drill-through tubing spool is installed on the wellhead housing. To perform the pressure tests, a bore protector sleeve is typically installed in the tubing spool through bore. The bore protector sleeve must be of sufficient thickness to be strong enough to withstand the test pressures without deforming.
The drill-through tubing spool through bore must also be protected as the equipment is run through the tubing spool prior to installing the tubing hanger. To protect the drill-through tubing spool bore wall, a bore protector sleeve may be inserted. A bore protector sleeve is also used to protect the drill-through tubing spool bore wall while the drilling string, casing strings, and casing hangers pass through the drill-through tubing spool. After the drilling operations are completed, the bore protector sleeve is pulled out of the drill-through tubing spool before the production tubing and tubing hanger are installed.
Although bore protector sleeves may be used for pressure testing and also protecting the tubing spool, the bore protector sleeve must have a large enough inner diameter to allow equipment to pass through the protector sleeve bore. In addition, the bore protector sleeve must have a small enough outer diameter to be retrieved from the drill-through tubing spool without removing the BOP. In addition, in the case of an offshore well, the bore protector sleeve must small enough to be retrieved through a drilling riser connecting the well to the water surface.
A drill-through tubing spool bore protector sleeve of sufficient size to withstand the pressure testing is too thick to allow the passage of equipment during drilling operations. One solution is to install a testing bore protector inside the drill-through tubing spool for pressure testing the drill-through tubing spool. After the testing is complete, the testing bore protector is removed from the drill-through tubing spool. Then, a drilling bore protector sleeve of a larger inner diameter is inserted into the drill-through tubing spool through bore to protect the tubing spool through bore during the drilling operations. The drilling bore protector sleeve is retrieved before the production tubing and production hanger are installed in the drill-through tubing spool. Thus, three “trips” are necessary, a first trip to remove the testing bore protector sleeve from the drill-through tubing spool, a second trip to install the drilling bore protector sleeve, and a third trip to remove the drilling bore protector sleeve.
Instead of using vertical trees, trees with the arrangement of production control valves offset from the production tubing, generally called horizontal trees, can be used. One type of horizontal tree is a Spool Tree™ shown and described in U.S. Pat. No. 5,544,707, hereby incorporated herein by reference. A horizontal tree also locks and seals onto the wellhead housing. In horizontal trees, however, the tubing hanger locks and seals in the tree bore. With the production valves offset from the production tubing, the production tubing hanger and production tubing may be removed from the tree without having to remove the horizontal tree from the wellhead housing. Horizontal trees have a larger through bore than a vertical tree and can thus allow the passage of larger equipment than vertical trees. A problem with horizontal trees, however, is that they are installed after the production casing has been installed in the wellhead. Therefore, horizontal trees require that the BOP must first be removed from the wellhead before installing the horizontal tree. After the horizontal tree is installed, the BOP is then installed onto the horizontal tree, thus requiring two “trips” to install the horizontal tree and the BOP.
The transverse bores of the horizontal tree, such as the production outlets and ports, as well as the transverse bore valves, need to be pressure tested at production operation pressures before producing well bore fluids. The pressure tests can be performed before and/or after the tree is installed on the wellhead housing. If the pressure tests are performed after installation on the wellhead housing, a means of preventing pressure from being applied downhole must be employed.
To perform the pressure tests, a bore protector sleeve is typically installed in the tree through bore. The bore protector sleeve must be of sufficient thickness to be strong enough to withstand the test pressures without deforming. In addition, the bore protector sleeve protects the tree through bore wall from equipment as it passes through the horizontal tree.
Another example of a horizontal tree is a drill-through horizontal tree. Drill-through horizontal trees also lock and seal on the wellhead housing, with the BOP landed on the drill-through horizontal tree. The production tubing hanger assembly locks and seals in the drill-through horizontal tree instead of in the wellhead housing. The drill-through horizontal tree has a large through bore for allowing equipment to pass through the tree bore. The large horizontal drill-through tree bore also allows the production tubing string to be pulled out through the BOP without disturbing the drill-through tree and the pressure integrity of the well. With a drill-through tree, the tree can be installed on the wellhead housing at the point when a BOP is needed for drilling. The problems associated with the vertical tree and the regular horizontal tree are solved with the drill-through tree because the well may be drilled and completed without pulling the BOP off the well for completing the well. Therefore, the well is always secure and only one BOP “trip” is necessary to drill and complete the well. Thus, the horizontal drill-through tree is also another type of drill-through spool body, with the addition of housing the production ports and valves.
However, the drill-through horizontal tree also presents problems to the drilling and completion operations. As with the regular horizontal tree, the transverse bores and respective valves of the drill-through tree need to be pressure tested. However, the pressure tests need to be run not only at production operation pressures, but also drilling operation pressures, before drilling the well and producing well bore fluids. The pressure tests can be performed before and/or after the tree is installed on the wellhead housing. To perform the pressure tests, a bore protector sleeve is also typically installed in the tree through bore. The bore protector sleeve must be of sufficient thickness to be strong enough to withstand the test pressures without deforming.
As with the regular horizontal tree, the drill-through tree through bore must also be protected as the equipment is run through the tree prior to installing the tubing hanger. A bore protector sleeve is also used to protect the drill-through tree bore wall while the drilling string, casing strings, and casing hangers pass through the drill-through tree. After the drilling operations are completed, the bore protector sleeve is pulled out of the drill-through tree before the production tubing and tubing hanger are installed.
Although bore protector sleeves may be used for pressure testing the tree and for protecting the tree, the bore protector sleeve must have a large enough inner diameter to allow equipment to pass through the drill-through tree through bore. In addition, the bore protector sleeve must have a small enough outer diameter to be retrieved from the drill-through tree without removing the BOP. In addition, in the case of an offshore well, the bore protector sleeve must be small enough to be retrieved through a drilling riser connecting the well to the water surface.
A drill-through tree bore protector of sufficient size to withstand the pressure testing is too thick to allow the passage of equipment during drilling operations. One solution is to install a testing bore protector inside the drill-through tree for pressure testing the drill-through tree. After the testing is complete, the testing bore protector is removed from the drill-through tree. Then, a drilling bore protector sleeve of a larger inner diameter is inserted into the drill-through tree through bore to protect the tree through bore during the drilling operations. The drilling bore protector sleeve is retrieved before the production tubing and production hanger are installed in the drill-through horizontal tree. Thus, three “trips” are necessary, a first trip to remove the testing bore protector sleeve from the drill-through tree, a second trip to install the drilling bore protector sleeve, and a third trip to remove the drilling bore protector sleeve.
In drilling a well, especially an offshore well, additional time can significantly raise the cost of drilling a well. To lower cost, some wells are drilled with only with the drilling bore protector installed. Installing the drill-through tree with only a drilling bore protector, however, sacrifices the ability to properly pressure test the drill-through tree transverse bores and valves such as with a test bore protector.
It is desired to properly test the drill-through tree connections, ports, and valves and also protect the tree through bore in a time and cost efficient manner. Consequently, to effectively test the drill-through tree transverse bores and valves and protect the tree through bore, the present invention has been developed. Other objects and advantages of the invention will appear from the following description.